scholarly journals Effects of Carbonate Minerals on Shale-Hydraulic Fracturing Fluid Interactions in the Marcellus Shale

2021 ◽  
Vol 9 ◽  
Author(s):  
Brennan Ferguson ◽  
Vikas Agrawal ◽  
Shikha Sharma ◽  
J. Alexandra Hakala ◽  
Wei Xiong
Keyword(s):  
Hydraulic Fracturing ◽  
Organic Contaminants ◽  
Produced Water ◽  
Marcellus Shale ◽  
Carbonate Minerals ◽  
Fracturing Fluid ◽  
Volatile Organic ◽  
Shale Formation ◽  
Temperature And Pressure ◽  
Hydraulic Fracturing Fluid

Natural gas extracted from tight shale formations, such as the Marcellus Shale, represents a significant and developing front in energy exploration. By fracturing these formations using pressurized fracturing fluid, previously unobtainable hydrocarbon reserves may be tapped. While pursuing this resource, hydraulic fracturing operations leave chemically complex fluids in the shale formation for at least two weeks. This provides a substantial opportunity for the hydraulic fracturing fluid (HFF) to react with the shale formation at reservoir temperature and pressure. In this study, we investigated the effects of the carbonates on shale-HFF reactions with a focus on the Marcellus Shale. We performed autoclave experiments at high temperature and pressure reservoir conditions using a carbonate-rich and a decarbonated or carbonate-free version of the same shale sample. We observed that carbonate minerals buffer the pH of the solution, which in turn prevents clay dissolution. Carbonate and bicarbonate ions also scavenge reactive oxidizing species (ROS), which prevents oxidation of shale organic matter and volatile organic compounds (VOCs). Carbonate-free samples also show higher pyrite dissolution compared to the carbonate-rich sample due to chelation reactions. This study demonstrates how carbonate minerals (keeping all other variables constant) affect shale-HFF reactions that can potentially impact porosity, microfracture integrity, and the release of heavy metals and volatile organic contaminants in the produced water.

In vitro cytotoxicity assessment of a hydraulic fracturing fluid

2015 ◽  
Vol 12 (3) ◽  
pp. 286 ◽  
Author(s):  
Madeleine E. Payne ◽  
Heather F. Chapman ◽  
Janet Cumming ◽  
Frederic D. L. Leusch
Keyword(s):  
Coal Seam ◽  
Hydraulic Fracturing ◽  
Human Health ◽  
Produced Water ◽  
Coal Seam Gas ◽  
Fracturing Fluid ◽  
Human Health Risks ◽  
Fracturing Fluids ◽  
Hydraulic Fracturing Fluid

Environmental context Hydraulic fracturing fluids, used in large volumes by the coal seam gas mining industry, are potentially present in the environment either in underground formations or in mine wastewater (produced water). Previous studies of the human health and environmental effects of this practice have been limited because they use only desktop methods and have not considered combined mixture toxicity. We use a novel in vitro method for toxicity assessment, and describe the toxicity of a hydraulic fracturing fluid on a human gastrointestinal cell line. Abstract Hydraulic fracturing fluids are chemical mixtures used to enhance oil and gas extraction. There are concerns that fracturing fluids are hazardous and that their release into the environment – by direct injection to coal and shale formations or as residue in produced water – may have effects on ecosystems, water quality and public health. This study aimed to characterise the acute cytotoxicity of a hydraulic fracturing fluid using a human gastrointestinal cell line and, using this data, contribute to the understanding of potential human health risks posed by coal seam gas (CSG) extraction in Queensland, Australia. Previous published research on the health effects of hydraulic fracturing fluids has been limited to desktop studies of individual chemicals. As such, this study is one of the first attempts to characterise the toxicity of a hydraulic fracturing mixture using laboratory methods. The fracturing fluid was determined to be cytotoxic, with half maximal inhibitory concentrations (IC50) values across mixture variations ranging between 25 and 51mM. When used by industry, these fracturing fluids would be at concentrations of over 200mM before injection into the coal seam. A 5-fold dilution would be sufficient to reduce the toxicity of the fluids to below the detection limit of the assay. It is unlikely that human exposure would occur at these high (‘before use’) concentrations and likely that the fluids would be diluted during use. Thus, it can be inferred that the level of acute risk to human health associated with the use of these fracturing fluids is low. However, a thorough exposure assessment and additional chronic and targeted toxicity assessments are required to conclusively determine human health risks.

scholarly journals Evaluation of anionic and non-ionic surfactant performance for Montney shale gas hydraulic fracturing fluids

2021 ◽  
Vol 11 (4) ◽  
pp. 1973-1991
Author(s):  
Sheau Chien Chee ◽  
Belladonna Maulianda Hidayat ◽  
Dzeti Farhah Mohshim ◽  
Zahidah Md Zain ◽  
Ivy Ching Hsia Chai ◽  
...  
Keyword(s):  
Surface Tension ◽  
Interfacial Tension ◽  
Hydraulic Fracturing ◽  
Reservoir Rock ◽  
Ionic Surfactant ◽  
Fracturing Fluid ◽  
Ph Change ◽  
Shale Formation ◽  
Soaking Test ◽  
Hydraulic Fracturing Fluid

AbstractHydraulic fracturing is often used in unconventional shale reservoirs, and 50%–95% of the injected hydraulic fracturing fluid remains in the formation due to the capillary effect. This phenomenon has been observed in the Montney shale formation, Canada, where the flowback water recovery is generally less than 25%. Surfactant is one of the hydraulic fracturing fluid additives for reducing surface tension and capillary forces to facilitate water flowback recovery. Surfactant loss due to adsorption by the reservoir rocks reduces the chemical’s efficiency, and this causes water retention in the formation and reduces water flowback recovery. The compatibility of surfactant with reservoir rock is critical to minimize surfactant adsorption on the rock surface because this diminishes the primary function of the surfactant hydraulic fracturing fluid additive and to ensure cost-effectiveness. This study evaluates surfactant efficiency to improve flowback recovery for the Montney shale formation based on IFT, surface tension, and adsorption. This study evaluates surfactant performance and performs a fluid–fluid interaction experiment and fluid-rock compatibility investigation. Several commercial surfactants are screened for low interfacial tension and surface tension. Further analysis is carried out by evaluating the fluid-rock compatibility using the static soaking test at reservoir pressure and temperature. The pre-soaking and post-soaking test fluids were analyzed for water composition, liquid–liquid interfacial tension, surface tension, and pH. Results showed that the selected surfactant is a critical determiner of the hydraulic fracturing fluid performance. SOLOTERRA 938 is an anionic surfactant that has good compatibility with Montney shale formation. Unlike other non-ionic surfactants, SOLOTERRA 938 retains the interfacial tension and surface tension after seven days of interaction with reservoir rock. The interfacial tension remained unchanged at 0.1 mN/m. The surface tension decreased from 28.4 to 27.5 mN/m with air and from 21.7 to 20.8 mN/m with hydrocarbon because surfactant behavior changes with pH change. The surfactant concentration was measured using high-pressure liquid chromatography, and the loss was 12% after seven days of interaction with the reservoir rock (from 0.1 to 0.088wt%). The adsorption calculated based on the concentration volume showed a low value of between 0.43 and 0.97 mg/g rock.

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